This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/JP99/00162 which has an International filing date of Jan. 19, 1999, which designated the United States of America.
The present invention relates to a low-sidestream-smoke cigarette capable of producing reduced sidestream smoke when the cigarette is smoked.
It is known that sidestream smoke from a cigarette can be reduced by lowering the inherent air permeability of the paper of the cigarette. For example, the inherent air permeability of the paper can be lowered by increasing the basic weight thereof.
However, the increase of the basic weight of the paper results in an increase of other pulp components in the entire cigarette than filler shreds, such as shredded tobacco. In this case, the cigarette cannot continue its static burning and worsens its flavor and taste. Moreover, high-basic-weight paper is poor in wrapping property or so-called roll-up property for the filler shreds, so that it is not suited for the production of cigarettes.
According to another known method for reducing the sidestream smoke from cigarettes, paper is loaded with a burning-retardant. This method considerably worsens the flavor and taste of cigarettes.
Further, methods are put to practical use in which magnesium hydroxide or calcium carbonate with a high specific surface area are used as loading materials (fillers) for paper. Since these methods causes the basic weight of the paper to increase, however, the roll-up property for the paper is poor and the flavor and taste is not agreeable. In connection with this, a double-wrapper cigarette is proposed in Jpn. Pat. Appln. KOKAI Publication No. 4-228059. This cigarette is provided with an outer wrapper, which is formed of paper containing a loading material of magnesium hydroxide and having an inherent air-permeability of 15 CORRESTA UNIT or less, and an inner wrapper, which contains tobacco material and has an inherent air-permeability of 50 CORESTA UNIT or more.
In the double-wrapper cigarette described above, the outer wrapper contains magnesium hydroxide, so that the flavor and taste of the cigarette worsens. Since the basic weight of outer wrapper increases, moreover, the outer wrapper has a problem on its roll-up aptitude. Since the inner wrapper has a high inherent air-permeability, furthermore, its effect of sidestream smoke reduction is low.
The present invention has been contrived in consideration of these circumstances, and its object is to provide a low-sidestream-smoke cigarette capable of reducing sidestream smoke without ruining its flavor and taste, combustibility, or roll-up property.
The above object is achieved by a low-sidestream-smoke cigarette of the present invention. This low-sidestream-smoke cigarette comprises a dual-structure wrapper that wraps filler shreds therein. An inner wrapper of the wrapper is formed of permeability-resistant sheet tobacco, while an outer wrapper is formed of cellulose-based paper. Permeability-resistant implies a low inherent air-permeability. The inherent air-permeability of the inner wrapper ranges from 0.1 to 8.0 CORESTA UNIT, and preferably to 5.0 CORESTA UNIT or less. The cellulose-based paper is paper that is formed of a cellulose base, such as flax pulp or wood pulp, loaded with a filler, such as calcium carbonate, and a burning additive, such as citrates, and may be ordinary cigarette paper that is commercially available.
According to the low-sidestream-smoke cigarette described above, the inner wrapper that is formed of a tobacco sheet is poor in combustibility. Since the outer wrapper is formed of ordinary paper, however, the outer wrapper is high in combustibility and serves as a burning assisting material for the inner wrapper. Thus, the low-sidestream-smoke cigarette can continue its static burning without the possibility of its burning cone dying unexpectedly.
Since the inner wrapper is permeability-resistant sheet tobacco, moreover, its inherent air permeability is low, so that production of sidestream smoke can be reduced considerably.
The sheet tobacco that forms the inner wrapper is papermaking sheet tobacco that is obtained by using the paper making technique or so-called slurry sheet tobacco that is obtained by drying slurry spread over a molding surface.
In the case where slurry sheet tobacco is used as the inner wrapper, the inner wrapper wraps the filler shreds therein in a manner such that its smooth surface on the molding surface side faces the filler shreds. In this case, a rough surface of the inner wrapper on the opposite side defines a large number of air cells between the inner wrapper and the outer wrapper. Air in these cells facilitates combustion of the inner wrapper, so that the static burning of the low-sidestream-smoke cigarette can be maintained securely.
The inner wrapper, which is formed of sheet tobacco, never worsens the flavor and taste during smoking, and inner wrapper itself can be flavored with ease.
Since the inner wrapper is formed of sheet tobacco, moreover, the inner wrapper as well as the outer wrapper is higher in roll-up property than paper that contains special additives.
Preferably, the respective basic weights and inherent air-permeability of the inner and outer wrappers are set as follows.
The basic weight and inherent air-permeability of the inner wrapper range from 30 to 80 g/m2 and from 0.1 to 8.0 CORESTA UNIT, respectively, and the basic weight and inherent air-permeability of the outer wrapper range from 15 to 30 g/m2 and from 15 to 100 CORESTA UNIT, respectively.
If the respective basic weights of the inner and outer wrappers are within the ranges described above, satisfactory roll-up properties can be secured for the inner and outer wrappers. Even if the air-permeability of the outer wrapper is large, since the air-permeability of the inner wrapper is within the aforesaid range, moreover, the air-permeability of the inner and outer wrappers as a whole is lowered, so that sidestream smoke can be reduced considerably.
Preferably, the inner wrapper is embossed at least partially. In this case, embossing the inner wrapper causes the substantial thickness of the inner wrapper to increase, which is conducive to the curtailment of shredded tobacco, and in consequence, to the reduction of production of sidestream smoke.
Preferably, moreover, the production of sidestream smoke from each cigarette is 10 mg or less, the speed of production of the sidestream smoke is 1.0 mg/min or less, and the tar content of each cigarette is 6 mg or less. In this case, low-sidestream-smoke cigarettes with reduced sidestream smoke and a light flavor and taste can be obtained.